阻抑动力学荧光法测定痕量间苯二酚

基于在ＨＣｌＯ４介质中,间苯二酚对Ｆｅ（Ⅲ）催化Ｈ２Ｏ２氧化罗丹明６Ｇ使其荧光猝灭的抑制作用,建立了动力学荧光法测定痕量间苯二酚的新方法。线性范围为０．００８～０．０９６ｍｇ／Ｌ间苯二酚,方法检测限为５．９ｕｇ／Ｌ。用于测定合成样中间苯二酚的含量,结果令人满意。     

Study on Arc Movement in Hollow Electrode Plasma Generators with Impressed Double Magnetic Fields

In order to prolong cathode lifetime of hollow electrode plasma generators, a method of impressed double magnetic fields with an alternating frequency is presented in this paper. The alternating frequency of the double magnetic fields is an important factor that influences the erosion rate on the area between the two coils' central planes. By analyzing the arc movement in the hollow cathode with a simplified theoretical model, the spiral curve shape of the radial arc and the relationship between the optimal alternating frequency and the intensity of magnetic fields are obtained. A photoelectric method is employed to measure the arc root rotation speed in the hollow cathode, and then the optimal alternating frequency is calculated as 319 Hz for the experimental conditions. The life testing with this alternating frequency showed that the cathode lifetime could be prolonged significantly.     

Highly sensitive voltammetric biosensor for nitric oxide based on its high affinity with hemoglobin

Although heme protein-based, amperometric nitric oxide (NO) biosensors have been well documented in previous studies, most have been conducted in anaerobic conditions. Herein we report a novel hemoglobin-based NO biosensor that is not only very sensitive but also usable in air. The heme protein was entrapped in a sodium montmorillonite film, which was immobilized at a pyrolytic graphite electrode surface. Film-entrapped hemoglobin can directly exchange electrons with the electrode, and this process has proven to favor the catalytic reduction of oxygen. In addition, NO induced a cathodic potential shift of the catalytic reduction peak of oxygen. This potential shift was proportional to the logarithm of NO concentration ranging from 4.0 × 10⁻¹¹ to 5.0 × 10⁻⁶ mol/L. The detection limit has been estimated to be 20 pM, approximately four orders lower than previously reported amperometric detectors.     

Low-temperature electrothermal vaporization of thenoyltrifluoroacetone complex of Sc(III) and Y(III) for sample introduction in an inductively coupled plasma atomic emission spectrometry,and their determination in biological samples

A new method for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of trace Sc and Y, based on gaseous compound introduction into the plasma as their thenoyltrifluoroacetone (TTA) complexes by electrothermal vaporization was developed. Using the reagent TTA as chemical modifier can not only enhance the analytical signals, but also reduce the vaporization temperature. At a temperature of 1,000 °C the trace Sc and Y can be vaporized completely into ICP. The factors affecting the formation of the chelate and its vaporization behavior, such as drying time, vaporization temperature/time, reaction medium and the amount of TTA, were investigated in detail. Under the optimized conditions (drying temperature/time 100 °C/10 s, vaporization temperature/time 1,000 °C/4 s), the limits of detection for Sc and Y were 19 pg and 34 pg (3), respectively, and the relative standard deviations for Sc and Y were 4.2% (c _Sc=0.2 g mL^–1; n=7) and 2.6% (c _Y=0.5 g mL^–1; n=7). The linear ranges of the calibration graphs cover three orders of magnitude. The method was applied to the analysis of the biological reference materials (GBW 07602, bush branches and leaves; GBW 07604, poplar leaves), and the results obtained were in good agreement with the certified values.     

Kinetics of the Thermal and Thermo‐Oxidative Degradation of a Polystyrene–Clay Nanocomposite

Summary: Thermogravimetry and differential scanning calorimetry have been used to study the thermal and thermo‐oxidative degradation of polystyrene (PS) and a PS–clay nanocomposite. An advanced isoconversional method has been applied for kinetic analysis. Introduction of the clay phase increases the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

The change in activation energy for the degradation of PS and the PS–clay nanocomposite with the extent of polymer conversion.     

Sensitive high-performance liquid chromatography/mass spectrometry method for determination of steviol in rat plasma

The main toxicological concern of stevioside, a highly potent sweetener from S. rebaudiana, is its main metabolite, steviol. To determine very low levels of steviol in in vivo experiments, a sensitive liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) method was developed for quantifying steviol in rat plasma after oral administration of a single dose of stevioside (0.5 g/kg). The sample preparation uses liquid-liquid extraction with tert-butyl methyl ether in an acidic environment. The retention time of steviol was 10.5 min. The assay was linear over the range 2-1000 ng/mL with a lower limit of detection of 1 ng/mL. The intra- and inter-day precision were <5 and <7%, respectively, and the accuracy was in the range 95-108%. The steviol concentration profile in rat plasma was determined.     

超高效液相色谱-串联质谱法快速检测洛党参中乙基多杀菌素残留

建立了超高效液相色谱-串联质谱(UHPLC-MS/MS)快速检测洛党参中乙基多杀菌素-J(XDE-175-J)和乙基多杀菌素-L(XDE-175-L)残留的方法。样品经乙腈提取,乙二胺-N-丙基硅烷和石墨化炭黑净化后,外标法定量。结果表明,XDE-175-J和XDE-175-L的峰面积与其质量浓度分别在0.075~75μg/L和0.025~25μg/L范围内,呈良好线性关系(r20.990);在0.375、3.75、75μg/kg加标水平下,XDE-175-J的平均回收率为88.4%~113.5%,相对标准偏差(RSD,n=5)为2.0%~4.2%;在0.125、1.25、25μg/kg加标水平下,XDE-175-L的平均回收率为84.4%~99.5%,RSD(n=5)为2.5%~4.9%。乙基多杀菌素的定量下限(LOQ)为0.375μg/kg(XDE-175-J)和0.125μg/kg(XDE-175-L)。该方法简便、快捷,灵敏度高,回收率和重复性良好,能满足农药残留检测技术要求,可用于大量洛党参样品中乙基多杀菌素的残留分析。     

Seasonal variations in metabolite profiling of the fruits of Ligustrum lucidum Ait

The metabolite profiling of fruits of the herb Ligustrum lucidum Ait collected during different months has been performed using ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC/QTOFMS) and multivariate statistical analysis techniques. The markers such as oleuropein acid, neonuezhenide, specnuezhenide, oleuropein and ligustrosidic acid accountable for such variations were identified through the loadings plot of principal component analysis (PCA), and the tentative identification of the markers is completed by comparing the mass spectra and retention times with those of reference compounds and/or tentatively assigned by matching empirical molecular formulae and MS/MS data with those of the known compounds published. Furthermore, one of the chemical markers, such as specnuezhenide, which is water-soluble, biologically active and also the predominant compound in this crude drug, was quantified by ultra-performance liquid chromatography coupled with a tunable UV detector (UPLC-TUV). The developed UPLC method provides good linearity (r(2)=0.9991), repeatability (RSD=2.96%), intra- and inter-day precisions (RSD=0.21%, 0.96%), with accuracies of 99.18-100.26% and a recovery of specnuezhenide of 97.57%. The fruits of L. lucidum Ait collected from August to December were tested. The results clearly show that the fruits of L. lucidum Ait harvested in October have the highest yields of specnuezhenide. It is also noted that the variations of content of specnuezhenide obtained by both methods have a strong correlation. This suggests that the newly proposed strategy is a reliable and simple method for the rapid discrimination of subtle variations, within the same plant species or strains, due to different seasonal collection times.     

Quality control of Citri reticulatae pericarpium: exploratory analysis and discrimination

Extracts of Citri reticulatae pericarpium (PCR) are commonly used in the Traditional Chinese Medicine. The quality control of PCR is currently performed by single marker analysis, which can hardly describe the complexity of such natural samples. In this study, a fingerprint methodology for PCR based on high-performance liquid chromatography (HPLC) was developed and validated. A total of 69 fingerprints of authenticated PCR samples, commercial PCR samples, mixed peel samples, and other Citrus peels were recorded. Exploratory data analysis allowed optimizing the extraction procedure and detecting mixed peel samples. Once the optimizations were performed and the method validated, discrimination between the authentic PCR samples and all other samples was performed by p-Discriminant Partial Least Squares. The established model was able to differentiate between classes with a high reliability for each sample. Furthermore, evaluation of the score and loading plots of the model indicated nobiletin, tangeretin, naringin and hesperidin as important markers for the quality control of PCR.